Method PerformLoopFor

source/script.cpp:10854–10933

ResultType Line::PerformLoopFor(ResultToken *aResultToken, Line *&aJumpToLine, Line *aUntil)
{
	ResultType result;
	Line *jump_to_line;
	global_struct &g = *::g; // Might slightly speed up the loop below.

	ResultToken enum_token;
	enum_token.InitResult(nullptr); // buf can be null because this isn't ACT_RETURN.
	PRIVATIZE_S_DEREF_BUF;
	result = ExpandSingleArg(mArgc - 1, enum_token, our_deref_buf, our_deref_buf_size);
	DEPRIVATIZE_S_DEREF_BUF;
	if (result != OK)
		// A script-function-call inside the expression returned EARLY_EXIT or FAIL.
		return result;
	
	int var_count = mArgc - 1;
	
	IObject *enumerator;
	result = GetEnumerator(enumerator, enum_token, var_count, true);
	enum_token.Free();
	if (result == FAIL || result == EARLY_EXIT)
		return result;

	// "Localize" the loop variables.
	auto var_bkp = (VarBkp *)_alloca(sizeof(VarBkp) * var_count);
	auto var_param = (ExprTokenType**)_alloca(sizeof(ExprTokenType*) * var_count);
	for (int i = 0; i < var_count; ++i)
	{
		ExprTokenType &token = *(ExprTokenType*)_alloca(sizeof(ExprTokenType));
		var_param[i] = &token;
		if (mArg[i].type == ARG_TYPE_OUTPUT_VAR)
		{
			auto var = VAR(mArg[i]);
			var->Backup(var_bkp[i]);
			token.symbol = SYM_OBJECT;
			token.object = var->GetRef();
			if (token.object)
				continue;
			result = FAIL;
			var_count = i + 1; // Restore var_bkp and free any previous refs.
		}
		// Omitted.
		token.symbol = SYM_MISSING;
		token.marker = _T("");
		token.marker_length = 0;
	}

	// Now that the enumerator expression has been evaluated, init A_Index:
	g.mLoopIteration = 1;

	if (result != FAIL)
	for (result = CONDITION_FALSE;; ++g.mLoopIteration)
	{
		auto enum_result = CallEnumerator(enumerator, var_param, var_count, true);
		if (enum_result == FAIL || enum_result == EARLY_EXIT)
		{
			result = enum_result;
			break;